On the early-time excess emission in hydrogen-poor superluminous supernovae

On the early-time excess emission in hydrogen-poor superluminous supernovae

On the early-time excess emission in hydrogen-poor superluminous supernovae

We present the light curves of the hydrogen-poor superluminous
supernovae (SLSNe I) PTF 12dam and iPTF 13dcc, discovered by the
(intermediate) Palomar Transient Factory. Both show excess emission at
early times and a slowly declining light curve at late times. The early
bump in PTF 12dam is very similar in duration (˜10 days) and
brightness relative to the main peak (2-3 mag fainter) compared to
that observed in other SLSNe I. In contrast, the long-duration (>30
days) early excess emission in iPTF 13dcc, whose brightness competes
with that of the main peak, appears to be of a different nature. We
construct bolometric light curves for both targets, and fit a variety of
light-curve models to both the early bump and main peak in an attempt to
understand the nature of these explosions. Even though the slope of the
late-time decline in the light curves of both SLSNe is suggestively
close to that expected from the radioactive decay of 56Ni and
56Co, the amount of nickel required to power the full light
curves is too large considering the estimated ejecta mass. The magnetar
model including an increasing escape fraction provides a reasonable
description of the PTF 12dam observations. However, neither the basic
nor the double-peaked magnetar model is capable of reproducing the light
curve of iPTF 13dcc. A model combining a shock breakout in an extended
envelope with late-time magnetar energy injection provides a reasonable
fit to the iPTF 13dcc observations. Finally, we find that the light
curves of both PTF 12dam and iPTF 13dcc can be adequately fit with the
model involving interaction with the circumstellar medium.

Abstract

We present the light curves of the hydrogen-poor superluminous
supernovae (SLSNe I) PTF 12dam and iPTF 13dcc, discovered by the
(intermediate) Palomar Transient Factory. Both show excess emission at
early times and a slowly declining light curve at late times. The early
bump in PTF 12dam is very similar in duration (˜10 days) and
brightness relative to the main peak (2-3 mag fainter) compared to
that observed in other SLSNe I. In contrast, the long-duration (>30
days) early excess emission in iPTF 13dcc, whose brightness competes
with that of the main peak, appears to be of a different nature. We
construct bolometric light curves for both targets, and fit a variety of
light-curve models to both the early bump and main peak in an attempt to
understand the nature of these explosions. Even though the slope of the
late-time decline in the light curves of both SLSNe is suggestively
close to that expected from the radioactive decay of 56Ni and
56Co, the amount of nickel required to power the full light
curves is too large considering the estimated ejecta mass. The magnetar
model including an increasing escape fraction provides a reasonable
description of the PTF 12dam observations. However, neither the basic
nor the double-peaked magnetar model is capable of reproducing the light
curve of iPTF 13dcc. A model combining a shock breakout in an extended
envelope with late-time magnetar energy injection provides a reasonable
fit to the iPTF 13dcc observations. Finally, we find that the light
curves of both PTF 12dam and iPTF 13dcc can be adequately fit with the
model involving interaction with the circumstellar medium.